1. Field of the Invention
The invention relates to an optical projection module, and more particularly to an optical projection module having an adjustment structure.
2. Description of the Prior Art
Referring to FIG. 1A, a conventional optical projection system 10 of well-known sequential color recapture technology includes a light source 11, a reflector 12, an integrated rod 13, a color wheel 14, a set of illumination lens 15, a light valve 16, a projection lens 17 and a screen 18.
The color wheel 14 consists of a red filter R, a green filter G and a blue filter B arranged in a helix. The light source 11 provides a light beam that reflects by a reflector 12 and then enters into the integrated rod 13 to perform uniformization. The light beam is filtered into red light 141, green light 142 and blue light 143 after passing through the color wheel 14. The color lights 141, 142, 143 are respectively in the shape of rectangular stripes, as shown in FIG. 1B. The color lights converge on the illumination lens 15 and then travel through the light valve 16 for color image processing. Finally, lights are projected via the projection lens 17 to form an image on the screen 18.
The rectangular stripes of R, G and B color lights 141, 142, 143 are projected on the light valve 16 at the same time. Therefore, the light valve 16 needs to simultaneously process digital signals with respect to R, G and B color lights. Furthermore, there are connected areas between the lights so that the processing of the digital signals has to be highly loaded to generate a clear image from the light valve 16. Referring to FIG. 2, the conventional optical projection system is constructed by assembling individual optical elements into the corresponding signal module, for which careful consideration is to be taken in respect of the positioning of the optical elements and prevention of dusts. The optical elements such as the integrated rod 13, the color wheel 14 and the light valve 16 are fixedly mounted in the projection system. After assembling, the optical elements can't be move to adjust for positioning. However, production and assembly tolerances existing in the system adversely affect the precise focus of R, G, B lights coming from the color wheel 14 on the light valve 16. Thereby, the light beams are not so clear, and the areas between the light beams entering the light valve 16 overlap one another. Due to overlapped areas with various color lights, the processing of the digital signals becomes more complicated. In order to simplify the processing of the digital signals, the conventional projection system usually does not process digital signals at the overlapped areas, which significantly reduces luminance and thus reduces luminescence efficiency.